Condition
Some customer may comment on the SES light on and a chuggle or surge. Diagnostics may show excessive TCC slip speed and DTC P0741 will be current code stored.

CauseSeal damage may allow the TCC apply fluid to leak into the channel plate, causing excessive TCC slippage under certain conditions, eventually causing no TCC apply.

TCC may have partial apply fluid pressure or no apply fluid pressure. If excessive slip speed is noted and condition/cause cannot be corrected by using DTC P0741 diagnostic chart, suspect worn seals from slippage of the drive sprocket bearing inner race on the drive sprocket.

Correction
DO THIS-----Repair the transaxle

DON'T DO THIS-----DO NOT replace the complete transaxle assembly

Follow the diagnostic and repair procedure below to repair this condition.

Remove the transaxle from the vehicle. Refer to the appropriate Service Information for transaxle removal procedure. Remove the torque converter.
Install the transaxle to holding fixture. Refer to Holding Fixture Installation SI Document ID #513730.
Remove the transaxle side cover, upper valve body and case cover. Refer to the appropriate Unit Repair Information in SI.

Inspect the two case cover seals (34 and 35) for uneven wear patterns.

Inspect the two case cover seals (34 and 35) for uneven wear patterns. The wear patterns will be evident by a uneven wear pattern of the inner diameter white seal surface as shown in the two above illustrations.

Inspect the two case cover seals (34 and 35) for splits/tears and or flat spots.

Inspect the support drive socket (400) for wear on the bearing race.
Inspect the case cover (33) for wear or damage due to the drive sprocket bearing spinning in the bore.

Important:

During the tear down inspection, pay particular attention to seals (34, 35, 409 and 412) for wear or damage.

Seals (34, 35, 409 and 412) are part of Gasket Kit, P/N 24221398, and do not need to be ordered separately.

Replace the Torque Converter when servicing a vehicle with this condition.
The Viscous Coupler has an extremely high failure rate when it is allowed to slip out of spec.

Re: Information on P0741 & P1860. 1998+

DTC P1860
A P1860 is a electrical circuit failure!

The PCM run a resistance check on the circuit. The TCC solenoid spec is 10 to 15 ohm's. The PCM controls the Ground side of the circuit. When ignition voltage is applied to the power side of the solenoid the voltage flows through the solenoid and enters the PCM on the control side. The PCM looks at the voltage and compares it to the battery/ignition voltage to determine the resistance of the Solenoid.
If the resistance is high or the circuit is open the PCM won't see enough voltage and this trips the Flag/DTC

Re: Information on P0741 & P1860. 1998+

P0741 = Failed Turbine Shaft Seals

A Viscous Coupler (VC) is a sealed unit. A TCC vc has clutch plates and a Silicone fluid in it. When the plates start rotating at two different speeds, the shear effect of the tabs or perforations on the fluid will cause it to heat up and solidify (Silicone when heated will turn into a near solid; the viscosity of dilatant fluids rapidly increases with shear). The fluid in this state will essentially glue the plates together and transmit power from one set of plates to the other. This increases the pressure inside of the sealed drum. If the pressure increases to much it will crack the VC drum.

Now you have bad seals and a bad VC.
This is very common and that is the reason GM states that the Torque Converter must be replaced.

I have seen several tech try to short cut this and not replace the TC. I don't think this has ever worked more that 5 times that I have seen in the last 5 years. They always come back with in a month and the tech has to do it over again.

Re: Information on P0741 & P1860. 1998+

GENERAL DESCRIPTION

As shown in figure 1, the 12.2 inch converter does not include a torque converter clutch. This type of converter is commonly referred to as an "open" converter. The 245 mm and 298 mm are sometimes referred to as a "closed" converter. The terms closed and open refers to the fluid flow through the converter with and without the use of a torque converter clutch (TCC).

Note: The torque converter operation in this book refers to the 245 mm and the 298 mm with the use of a TCC. However, the differences with the 12.2 inch (310 mm) "open" converter are pointed out as appropriate.

TORQUE CONVERTER ELEMENTS

The torque converter assembly serves three primary functions. First, the torque converter is a fluid coupling that smoothly transmits engine torque to the transmission gear-train. This fluid coupling also allows the vehicle to stop without stalling the engine. Secondly, it multiplies torque. from the engine to the transmission for additional vehicle performance. Finally, the torque converter assembly provides a mechanical (or direct drive) link from the engine to the transmission with the use of a torque converter clutch (TCC).

A 245 mm or 298 mm "closed" converter has four elements (Fig. 2). This design contains a converter pump assembly (driving member - I), a turbine assembly (driven or output member - F), a clutch pressure plate assembly (C) splined to the turbine to provide direct drive, and a stator assembly (reaction member - G). The converter cover (A) is welded to the pump to seal all four members in a fluid filled housing. The 12.2 inch (310 mm) "open" converter has three elements. This design contains a pump (I), turbine (F), and stator (G), but does not have a clutch pressure plate assembly.

The converter cover (A) is bolted to the engine flex -plate which is bolted directly to the engine crankshaft. Therefore, the converter pump is mechanically connected to the engine and turns at engine speed whenever the engine is operating.

The converter pump (I) acts as a centrifugal pump, picking up fluid at its center and discharging this fluid at its rim between the blades (Fig. 3). It is the force of this fluid from the pump hitting the turbine blades that causes the turbine to rotate. When the engine is idling in gear, the converter pump is not spinning fast and the force of the fluid leaving the pump is not great enough to turn the turbine and move the vehicle. As engine speed increases, fluid force increases and more engine power is transmitted to the gear train. Turbine speed does not reach engine speed until the torque converter clutch (pressure plate) is applied. Thus, there is a small amount of slippage in this fluid coupling between the converter pump and turbine.

The pressure plate (C) is splined to the turbine hub. It applies against the converter cover to provide a mechanical (direct drive) coupling of the engine to the transmission. This mechanical coupling provides a more efficient transfer of engine torque to the drive wheels by eliminating the small amount of slippage that occurs in a fluid coupling. Thus, with the pressure plate (TCC) applied, the turbine assembly turns at engine speed and torque is no longer being multiplied.

To aid in torsional shock during converter clutch apply, a damper assembly (D) is used with the converter clutch pressure plate (C). The spring loaded damper assembly is splined to the converter turbine assembly (F). The converter clutch pressure plate is attached to the pivoting mechanism of the damper assembly. This pivoting action allows the pressure plate to rotate independent of the damper assembly, up to approximately 45 degrees. The rate of independent rotation is controlled by the pivoting mechanism acting on the spring in the damper assembly. The cushioning effect of the damper assembly springs aid in reducing converter clutch apply feel and irregular torque pulses from the engine or road.

The stator (G) is located between the converter pump and turbine and is mounted on a one way roller clutch. The purpose of the stator is to redirect the flow of fluid returning from the turbine to assist the engine in turning the converter pump. This redirection increases the force of the fluid driving the turbine and, as a result, multiplies torque from the engine (Fig. 4). If the fluid from the turbine was not redirected at low vehicle speeds it would impede the rotation of the converter pump.

At low vehicle speeds, when greater torque is needed, fluid from the turbine hits the front side of the stator blades (converter multiplying torque). Because the roller clutch holds the stator from moving in that direction, fluid is redirected from the turbine to assist the engine in turning the converter pump. Fluid from the converter pump then has more force to turn the turbine assembly and multiply engine torque.

As vehicle speed increases, centrifugal force changes the direction of fluid from the turbine. The direction of this fluid is such that it hits the back side of the stator blades (converter at coupling speed). This causes the roller clutch to overrun and allows the stator to rotate freely. Fluid is no longer redirected and engine torque is not being multiplied

TORQUE CONVERTER CLUTCH

As mentioned previously, the torque converter is not 100% efficient (up to a 10% loss) at coupling speed without the TCC applied.

The energy from the engine is wasted by the torque converter in the form of heat. This heat created by the slippage between the converter pump and turbine is the largest source of heat for transmission fluid. Thus, if this energy can be captured, we could increase the fuel economy of the vehicle and also reduce transmission fluid temperature. The torque converter clutch performs this task. The converter clutch functions similar to a standard transmission clutch by mechanically connecting the engine to the transmission. This makes the torque converter 100% efficient, thus increasing fuel economy and reducing transmission fluid temperature. The actual speed at which the TCC applies varies between vehicle applications.

There are three types of pressure plates in the present Hydra-matic converter assemblies. Two of these have spring type torsional dampening and the third has a viscous torsional dampening.

With the spring type damper, (Fig. 2), as the TCC applies, the springs in the damper assembly compress and allow the pressure plate to pivot. The pressure plate is allowed to pivot independently of the turbine to approximately 45 degrees. The spring cushioning effect aids in reducing the converter clutch apply feel.

A poppet style pressure plate is used with diesel engine applications (Fig. 5). With this type of pressure plate the

spring damper uses additional fluid control valves. These valves equalize fluid pressures on both sides of the pressure plate during TCC disengagement. This allows the pressure plate to release quicker and reduce torsional vibrations during deceleration on diesel applications.

VISCOUS CONVERTER CLUTCH

The third type of pressure plate is the viscous converter clutch (Fig. 6). The viscous clutch is only used on some HYDRA-MATIC 4T60 and 4T80 transaxles to provide a smoother apply feel. The viscous converter clutch performs the same functions as the conventional converter clutch explained earlier. The primary difference between the converter clutch and the viscous converter clutch is the method of dampening the apply feel. In the viscous clutch the spring damper is replaced by using viscous (thick) silicone fluid sealed between the body and cover of the clutch assembly. This fluid provides a smooth apply of the clutch assembly when it engages with the converter cover.

When the viscous clutch is applied (Fig. 7) the silicone fluid grips the intertwined ridges of the body and rotor of the viscous clutch. With the rotor splined to the turbine hub this forces the turbine to rotate at nearly the same speed as the converter cover. With this viscous apply there is still a minimal amount of slippage between the rotor and body.

Re: Information on P0741 & P1860. 1998+

AJ,

Thanks for this most valuable information. I knew of the directive, but did not know the details.

A dealership has my transaxle out right now. I went to look at it yesterday and the O.D. of the drive sprocket is scored and the seals are wiped out. I was hoping to only replace the solonoid. It was in fact the soleniod was toasted to a crisp.

Logan noted in his posts that he in fact felt his solenoid fail and replaced it right away. The tech explained to me that the low control pressure from the leaking internal seals in effect lead to the solenoid failure due to the increased band width imposed on the solenoid. I drove mine about 1,500 mi in this condition.

It will be interesting to see if Logan's repair hangs in there for the long haul. I wish him Luck.

Remember "If you want to drive like a sport, you will pay like a sport"
Blue_Eldo

Re: Information on P0741 & P1860. 1998+

Originally Posted by blue_eldo

AJ,

Thanks for this most valuable information. I knew of the directive, but did not know the details.

A dealership has my transaxle out right now. I went to look at it yesterday and the O.D. of the drive sprocket is scored and the seals are wiped out. I was hoping to only replace the solenoid. It was in fact the solenoid was toasted to a crisp.

Logan noted in his posts that he in fact felt his solenoid fail and replaced it right away. The tech explained to me that the low control pressure from the leaking internal seals in effect lead to the solenoid failure due to the increased band width imposed on the solenoid. I drove mine about 1,500 mi in this condition.

It will be interesting to see if Logan's repair hangs in there for the long haul. I wish him Luck.

Remember "If you want to drive like a sport, you will pay like a sport"
Blue_Eldo

We see a lot of P0741 with a P1860 also.
Sometimes the P1860 has not set, but you touch the burnt solenoid and the end falls off of it.
When the solenoid is new it is grey. When they are burnt they are brown.
Now the reason they burn up. Hmmm. Two thoughts on that. First is the TCC Solenoid cause the P0741. The other is the PCM has to drive the TCC Solenoid harder to compensate for the bad seals. I say it is the second. The side cover may have been machined slightly off center and caused the seals to wear irregularly first.

Re: Information on P0741 & P1860. 1998+

On a non VC TCC clutch you have a center section (Dampener Assembly) that is similar to one used on Manual Trans Clutch Disc. It uses Tortional Springs

On a VC the center section is a sealed unit/drum that allows for a softer engagement and a large/gross amount of slippage under load. The more it slips the hotter the Viscous fluid gets and this causes it to lock up. It also can cause so much pressure in the VC sealed unit it cracks.

Re: Information on P0741 & P1860. 1998+

I had my 97 Eldorado done by Tranny shop reffered them to GM's Reccomendations. Replaced the Input solenoid, Tc solenoid, TC, the O ring on the gasket on the rear input shaft caused the leak. It seems you just have drop the tranny and look at it. Done for $1698. 931. was for labor. Bad batteris play havoc with these trannys, and Alternators. I also had replace the alternator, because previous ower put in incorrect battery size to small. The battery was also at 50% capacity these trannys are electronic, they need the correct power. I notice immediate improvement, by changing battery, in stering, and driveability of the car. See full post under tc po741

Re: Information on P0741 & P1860. 1998+

I am very busy with everything especially the house right now, but I have been thinking about a new tune.
I would shut off the TCC, P0741 DTC and set up a Lean Cruise patch that I have to get better fuel mileage. I would have to be very careful not to go too lean because it would take out the Cat. The Lean Cruise patch was running about 16 to 1 afr and we had NO misfires.

Re: Information on P0741 & P1860. 1998+

Yeah, but these guys are talking about different engines in different platforms with different transmissions, so how do you adapt the "lean cruise" patch to a 2000 - 2004 N*/4T80E FWD package ???

GM designed it, I found a copy of one of them years ago.

Driving 65 mph in a 55 mph is illegal and partially for the same reason (Emissions). I am sure you remember those add campaigns telling every one to slow down? You would get X amount of better fuel economy and reduce the emissions out put if you slow down.